Currently, emphasis of the criteria for rating a web site is on the metrics of the popularity of the web site, e.g., PageRank ranking of Google, web site ranking of Alexa, etc.
The basic idea of the PageRank ranking of Google is that the popularity of a web site is proportional to the number of web sites that link to the web site and the popularity of the web sites that link to the web site. The specific calculation formula thereof is as follows:
                              PR          ⁡                      (            u            )                          =                              d            ·                                          ∑                                  v                  ∈                                      L                    ⁡                                          (                      u                      )                                                                                  ⁢                                                          ⁢                                                PR                  ⁡                                      (                    v                    )                                                  /                                  N                  ⁡                                      (                    v                    )                                                                                +                      (                          1              -              d                        )                                              (        1        )            where PR(u) denotes the PageRank value of a web site u, L(u) denotes a set of web pages that point to the web site u, N(v) denotes the number of outbound links from a web page v, and d denotes an attenuation factor, the value of which is between 0 and 1, and typically is 0.85.
The web site ranking of Alexa determines the popularity of a web site by calculating the accumulated number of reaches to the web site and average page views of the users in recent three months.
However, with the popularity of the network, network security problems also become increasingly severe, and malicious accidents of phishing, fraud, and propagation of Trojan viruses emerge one after another, while the above criteria of evaluating the popularity of a web site are not efficient enough to mark the security degree of a web site. Even a web site with high popularity may also be a web site hung up with Trojans or a phishing web site after it is hacked by a hacker, thus threatening the security of the users.
Currently, there have been some third parties who mark the security degree for web sites, wherein a famous one is such like the “credible web site” validation released by the company knet.cn, it marks the reputation of web sites by manual checking and charges a certain amount of annuity fees for web sites that have passed the validation. However, there are a lot of limitations in marking web sites by using such a kind of black-and-white list:
firstly, the application range thereof is relatively small, and mainly aims to profitable enterprises' web sites, while there is not enough motivation for personal web sites and non-profitable enterprises' web sites to pay for this kind of validation;
secondly, for web sites whose security information is under unknown status, it cannot help the user to efficiently distinguish malicious web sites from safe web sites; and
furthermore, even if a web site has passed the validation, it may also issue falsity information after it is frequently hacked by hackers as to being hung up with Trojans or the web pages thereof are changed, and thus simple manual authorization cannot respond to dynamic changes of the content of the web sites on time.